Liter



P 1963 0. Q. NIEHAUS 3,103,573

RESISTIVE HEATER CONTROL METHOD Filed June 2'7, 1962 4 Sheets-Sheet 1 AC D6 A6 vomas 52 72 ,22; 16 01/47/01 momma SOURCE POM/1? POM Elf GOU/PCE com/W01. 16/,1

2 RESIST/V5 HEATER \coMpz/rf/z 17 a I \i I 19 as 2/1 2+ 2/2 .25 5.2 ,29 55 HA7fi HEA rm AC ELECTRIC/1L DC 146 DC VULMEE POWER POWER momma momma/v sawrcs SUURC'E CONTROL 51 2o REs/sm/E HATER mam/me INVENTOR OWEN Q. N/EHA U6 ATTORNEY Sept. 10, 1963 0. Q. NlEHAUS 3,103,573

RESISTIVE HEATER CONTROL METHOD Filed June 27. 1962 Sheets-Sheet 2 INVENTOR OWE/V Q. N/EHA us BM m /54m ATTORNEY Sept. 10, 1963 0. Q. NIEHAUS RESISTIVE HEATER CONTROL METHOD 4 Sheets-Sheet 3 Filed June 2'7, 1962 INVENTOR OWE N Q. N/EHA U5 8% ATTORNEY 4 Sheets-Sheet 4 INVENTOR ATTORNEY k Q\b ma w. 1 l l I Ill. t llil i NE QM K23: n

7 7 W|II1IL r|i1L \QH \wH \w Sept. 10, 1963 0. Q. NIEHAUS RESISTIVE HEATER CONTROL METHOD Filed June 27, 1962 OWEN Q. N/EHA us ling resistive heater temperatures independently of ambientltemperature.

This application is a continuation-impart fofcopending applications Serial Number 10,3 78, now abandoned, for Method for Control of Resistive Heater, filed February 23, 1960, and Serial Numberl89,l 5l, now abandoned, for Improved Method for} Control of Resistive Heater, filed February 14, 1961.

United States Patent .0

The prior art teaches elaborately dependent means for I measuring resistance in a heater element circuit so as to control temperatures in a mass... surrounding the heater elements. The present invention is distinguishedfrom such means in that an-isolated circuit is employed to independently measure resistance in the heater element itself and without reference {to the current and voltage properties of the heate'r 'circuit.

3,103,573 Patented Sept. 10, 1963 peratur-e control not achievable by the properties of the refrigeration. or cooling system. Such a cooling jacket might serve the purpose of dropping temperatures 60 F. below room. temperature (:5" F.) and the heater might beused to control a smaller internal volume at say 40 F. below room temperature (i /z F.).

Accordingly, it is an object of invention to provide a method for controlling temperature in a resistive heater; independently of ambient temperature.

Another object of invention is to provide a method for independently measuring resistance in a resistive heater.

Another object of invention is to provide a method for independently measuring resistance in a heater and varying energization of said heater to provide substantially constant heater resistance and temperature.

Another object of invention is to provide an isolate A.C.- voltage circuit for independently measuring resistance in'a D.C. powered heater.

Another object of invention is to provide a method for utilizing a DC. voltage circuit for independently measuring' resistance in an A.C. powered heater.

' Yet another object of invention is to provide a method for controlling temperature in a first frequency A.C.

I The invention accordingly consistsin a method-foiflconv trolling aresistive heater comprising the steps of ener-j gizing' the heater, independently measuring resistance ,in the heater by means of an isolated circuit, and varying the energization so as to maintain substantially constant i temperature in the resistance. 1

The present method isapplicableto control of rain; I

p'erature in resistive heaters which have resistive proper-j ties 'correlated' with heater temperature. Thus, resistance encountered in such a heater ismeasured by a ,sepa rately' energizedandisolated circuit in terms of' apre selected resistance accompanying a desired temperature in the heater. Accordingly}energiaationof the resistive h e ater'circuitmay be limited" so as to m-aintain hea ter resistance and thus heater temperature substantiallyfcom stant with respect to a preselected resistance temperature Vallie. I i

As' further distinguished trom'the prior art, the present method of temperature'control by independently measluring and controlling resistance in a heater does-not imply control of electricalpower. Merely controllingeledtiical power to a constant value does not necessarilyimply controllingtemperature of a resistive heater since the temperature of a resistive -heater-iis related to 'rate of of second frequency A.C.

Yetadditional objects of invention will become apparent from the ensuing specification andatta' 'ched drawings-wherein:

FIG. -1 is a schematic of a DC. powered resistive heater which is temperature-controlled by independently measuring-resistance in said heater through anisolated A.C. voltage circuit and varying, accordingly, energization of said resistive beaten I FIG. 2 is a schematic of an] A.C. powered resistive heater which is temperature-controlled'by independently measuring resistance in said heater through an isolated DC. voltage circuit and varying, accordingly, energizecontrolled by independently measuring resistance in said heat er through an A.C. voltage-source of'a second frequency and varying, accordingly, energization of said resistive heater circuit. a V g FIG. 4 is a schematic of a resistive heater powered by an electrical energy source and temperaturecontrolled heat transfer between the heater and mass of material being heated and/or between the heater and its environ It is suggested that the present method .of temperature v control "in a resistive heater would be applicable in thermal suture bonding devices heating elementsin elec- 'trickitchen ranges, domestic heating'pads,;.electric blah; I ket s, space and crash helrnet face plate lieat v fogging devices and all other'deVices' where itisj des-irable to control "or" regulate resistive heatergtemperature "i nd de dependently of ambientjftemperature. f 1; Also, the presentmethodis'applicable to control or temperatures in resistance cooling devic' below ambient temperature by independently measuring resistance in the coolingelement and, accordingly,lvaryv a v suchfas l eltier Y iunctions,where within the cooling capability of thejunc-i tihnit'is possible to establish andgrnaintaintemperatures by independently measuring resistance in said heater through a voltage source of same or other source as the heater electrical power source and varying, accordingly, energization of said heater circuit. According to this modification, a commutator provides time sharing of circuit elements '61, 56 and "62.

FIG. 5 is a detailed schematic of "resistive heater and independent measuring circuits of FIG; 1.

FIG. 6 is a detailed schematic of a resistive heater and independent measuring circuits of FIG. 4. a

FIG)? is a detailed schematic of the FIGS. 1 and 5 resistive heater circuit modified to. the extent that the capi-tor is removed from the A.C. isolation means 4 and located in DC. power source 1 7 I FIG. 1 illustrates the present method of controlling through an i'solatedconstantAC. voltage source the resistance of a DC. energized heater. "Heater power source 1 supplies DC. power to resistive heater 2, having either a positive :or negative temperature co-efiicient or resistance, through a circuit comprising heater electrical power control 3 and an A.C.-; isolation means" 4 and suitable electrical conductors 5, .6, 7, 8, 9, and 10.

The resistance of heater 2 is measured independently by an isolated circuit comprised of DC. isolation means 11,

l A.C. voltage source 12, computer 13 and suitable electams a resistance heating element, positioned for tem- 'trical conductors 14, 15, 16, 17, 8, and 9. Any difference between said heater 2 resistance and a preselected reference resistanceis computed in computer 13. and thence relayed, through suitable electrical, mechanical or other means 18, .tothe heater electrical power control 3 which varies energization of resistive heater 2 to reduce the aforementioned resistance difference :to essentially. zero. concomitantly A.C. power is blocked from the resistive heater circuit by. A.C. isolation means 4. Conversely in r 3., The direction of motor M rotation is controlled. by

amplifier A whichtreceiv-es its intelligence via conductors 18 from computer bridge circuit 13. In A.C. voltage source 12 power such as 60 cycle per second, 115 volts, is supplied to they-terminals and is-altered as required by power transformerT. Thesecondary of transformer T- provides A.C. energization through conductors 16 to computer bridge circuit 13. The resistive heater 2' DC.

The capacitor shown in dependent A.C. isolation means'40 and suitable electrical energy is blocked or; isolated from computer bridge circuit 13 by condenser C in D.C. isolation means 11. A.C.

energy used to energize computer bridge circuit 13 is blocked or isolated from the heater D.C.,powerv source 1 by inductor L1in A.C. isolation means 4 and capacitor .C, which as described above maybe located in either heater D.C. power source ,1 or in A.C. isolation means 4, as shown in FIG. 5. InductorL and capacitor C function as a low pass filter; Any difference between resistive heater -Z. resistance "and a preselected, controllable resist isolation means58, a voltage source, either A.C..or D.C., 5 64, fa computer 65 and suitable electrical conductors 61, i n 66, 67, 68,"and 62;- The commutator 58 permits time sharing fof 'circuit elements 6'1, 5'6, 62 between the,

heater energizing circuit. and the heater resistancev measprising heater electrical power control 39, a frequency conductors 41,42, 43, 44, 45 and 46-. The resistance of heater 38 is measured by an isolated circuit comprised of frequency dependent A.C. isolation device 47, A.C. second frequency voltage source 48, computer 49 and suitable electrical conductors 56,51, 52; 53, 44, and 45. Any difference between said heater 38 resistance and a I preselected reference resistance is computed in'cornputer 49 and'thence relayed through suitable electricahmechanicalor other means 54 to the heater electrical. power control '39 which, in turn varies energization of heater so as to reduce [the aforementioned resistance difference, to essentially zero. Frequency dependentsAC. isolation.

device permits the passage of =A. C., first frequency but blocks A.C. secondfrcquency supplied in the isolated circuitby A.C. voltage source 48. v FIG. 4 illustrates a modified method of controlling an electrically energizedheater 56 through the vuseof ant' isolated voltage circuit for; measuring the resistance of heater 56. Heater '56 may possess eitheranegative; or

Heater positive temperature coefiicient of resistance. electrical power source 55 supplies electrical power, either A.C. or D.C. to resistive heater 56 mhrougha circuit comprising heatereleetrical power control 5 ?7, a commutator isolation means 58 andasuitableg electrical conductors. 59,

60, 61, 62., and 63. The resistance of heater t56 is mea s ured by an isolated circuitcomprised of the commutator t wing-circuit] Commutator 58 may be any suitable'elecance of rheostatRz, unbalances computer bridge circuit 1 13; This unbalance provides driving intelligence through amplifier Ato motor Min heater electrical power control 3, to alter rheostat R1, which'thcn varies the electrical energy supplied to the resistiveheater 2. This, in turn, appropriately changes the temperature and hence the resistanceof'resistive heater- 2 to, bring the latter into substantial agreement with the preselected value of ,resistor RZin computer bridge, circuit 13.

FIG. 2 illustratesa ,rnodified method of controlling A.C. energized heate'r' 20 through the use of an isolated D.C. voltage circuitformeasuring the resistance of heator other means 69 to the heater eleotri calpower control trioal or mechanical device icapable of closing either the heater energization circuit orl'the heater resistance, ineas uring circuit but not. both simultaneously. YAny differ W ence bet-ween the said heater-56 resistance and a prese- I lected reference resistance is computed in computer 65 when the heater resistance measuring circuit is closed and thence relayed through suitable electrical, mechanical '57 and, thus, reduce the aforementioned resistance differ-1- ence to essentially. zero. FIG. 6 setsforth a typical circuit capable of performing functions described for :FIG.

4. Heater electrical power source 55 embodies a D.C.

battery. The D.C. battery may alternatively be supplanted by an A.C. power adapter shown in phantom,

er 20. Heater 20,may possess either a negative or lpositive temperature coefficient ofresistancer Heater A.C. powersource l9 supplies A.C. power to resistive heater 20 throughya circuit comprising heater electrical .power control21, D.C..isolation means 22 and suitable electricalv providing for example 60 cycles per second, 'llsyolt'si In t the former case, the battery voltage applied to resistive.-

heater 56 is appropriately varied by heater electrical power control 57 motor MdrivingrheostatRll; Motor M is conductors 23, 24, 25,26, 27,;andf28r The resistance of heater 20"is measured, by an. isolated circuit comprised of L A.C. isolation device 29, DC. voltage source 30, computer 31 and suitable electrical conductors 32, 33, 34,

35, 26, and 27. Any dillerence between the said heater 20 resistance and a preselected reference resistance is computed in computer 31 andthence relayed through suitable electrical, mechanical or othermeyans 36,110 heatcurrent. but blocks the D.C. power supplied by the D.C. voltage source,.3ll-. AC. isolation device 29 permits. the passage of direct current, but blocks A.C. originating from the heater A.C. power source, 19.

FIGQ3 illustrates a modified method for controlling an heater resistance'through an isolated A.C. circuit. HeaterA.C. power source 37 supplies AC. power of a first frequency to resistive heater 38 through a circuit comcontrolled by amplifier A which receives its-intelligence via conductors I69fnomcomputer bridgecircuitoi I i 5 mutator 58 provides electrical isolation between the heater g energizing circuit shown to theleft of resistive heater 56;,

and the heater resistance measuring circuit shown to the right of heater 56and is comprised of a constant speed motor M, which drives a commutator wiper in a counter rection of rotation-is immaterial to the proper function? ing' of laser-r am: The commutator wiper alternately l i v closes the -heater;cnergizin-g circuit the :heater re-. sistanc'e measuring circuit. length of time the heater .er electrical power control 21 in such manner as to vary energization cff heater 20 and, thus, reduce the afore-- mentioned resistance difference to essentially zero. D.C. isolation device 22 permits the passage of A.C. heater prising a DC. battery, which is introduced'into there n ance measuring circuitt'b-y' a rotaryswitoh. Therot-ary I.

7'5 switch is mechanically driven'iri synchronism withjthe':

clockwise direction in thecircuit shown. The actual d" energizing circuit is closed canb'e'seenito be appreciably longer than the length of time the heater resistance meastiring circuit'is closed; This is a design'yariable, to be judiciously chosen ito satisfy particular heater requir rnents'l Whilean electromechanical commutator,"

Y 70 A.C. energized heater, which may be either a negative or positive temperature coefiicient material, by measuring shown it may be readily replaced with anallelectron counterpart." Heater electrical resistanceis measured by a circuit energized'by voltage source 64'," shown as om closing or the heater resistance measuring circuit by the commutator 58 motor M. When inserted, voltage source 64 battery energizes computer bridge circuit 65. One leg, R2, can be preselectively. controlled. Bridge unbalance arises when the resistance of heater 56 differs firom the set resistance of rheostatRZ. This unbalance is transmitted through conductors 69 to heater electrical power control 57 amplifier A to rotate motor M, and rheo'stat R1, thus varying the heater energy supplied by the heater energizing circuit which in turn varies the heater temperature and simultaneously its resistance in such manner as to bring its resistance into agreement with computer bridge circuit rheostat R2.

As will be apparent, the present method of controlling temperature in a resistive heater by independently measuring resistance in said heater and varying energization of said resistive heater so as to maintain substantially constant resistance and thus temperature in said resistive heater is applicable to temperature control of the above described devices as well as control of various other resistive heating means, indeepndently of ambient temperatures. Applicant does not intend to be limited by the individual elements illustrated and described in the suggested circuits; There are literally thousands of variations in circuitry and interchanges of elements which might be resorted to without departing from the spirit and scope of the invention, as defined by the subjoined claims.

I claim:

1. A method for control of a resistive heater having a temperature coefficient of resistance to the extent that temperature changes in the heater are reflected in measurable changes of resistance in the heater, independently of ambient temperature comprising energizing a resistive heater circuit; energizing an isolated measuring circuit; measurng resistance in said resistive heater through said isolated measuring circuit and in terms of preselected resistance accompanying desired temperature in said resistive heater; and varying energization of said resistive heater circuit so as to maintain said pro-selected resistance and, thus said desired, temperature in said resistive heater.

2. A method for control of resistive heater temperature independently of ambient temperature, which said 6 resistive heater has resistive properties correlative with heater temperature to the extent that temperature changes in the heater are reflected in measurable changes of resistance; comprising energizing a resistive heater circuit; energizing a voltage isolated measuring circuit; measuring resistance in said resistive heater through said isolated measuring circuit and in terms or preselected resistance accompanying desired temperature in said resistive heater; and varying energization of said resistive heater circuit so as to maintain said pro-selected resistance and, thus said desired, temperature in said resistive heater. 3. A method for control of resistive heater temperature independently of ambient temperature as in claim 2, said energizing of said resistive heater circuit being through a DC. power source and said energizing of said isolated measuring circuit being through an A.C. voltage source.

4. A method for control of resistive heater temperature independently of ambient temperature as in claim 2, said energizing of said isolated measuring circuit being through a DC. voltage source.

5. A method for control of resistive heater temperature as in claim 2, wherein said energizing or said resistance heater circuit is by means of an A.C. first frequency power-source and said energizing of said isolated measuring circuit is by means of an A.C. second frequency power source.

6. A method for control of resistive heater temperature as in claim 2, including time sharing electrical energy of said circuits through said resistive heater.

7. A method for control of resistive heater temperature as in claim 2, including separately commutating electrical energy of said heater and isolated measuring circuits through common portions of said circuits.

References Cited in the file of this patent UNITED STATES PATENTS 1,566,980 Seede Dec. 22, 1925 1,913,580 Altshuler et al. June 13, 1933 2,158,135 MacFa-rlane May 16, 1939 2,284,863 Gulliksen June 2, 1942 2,694,133 Hack Nov. 9, 1954 2,769,076 Bogdan Oct. 30,1956 

1. A METHOD FOR CONTROL OF A RESISTIVE HEATER HAVING A TEMPERATURE COEFFICIENT OF RESISTANCE TO THE EXTENT THAT TEMPERATURE CHANGES IN THE HEATER ARE REFLECTED IN MEASURABLE CHANGES OF RESISTANCE IN THE HEATER, INDEPENDENTLY OF AMBIENT TEMPERATURE COMPRISING ENERGIZING A RESISTIVE HEATER CIRCUIT; ENERGIZING AN ISOLATED MEASURING CIRCUIT; MEASURING RESISTANCE IN SAID RESISTIVE HEATER THROUGH SAID ISOLATED MEASURING CIRCUIT AND IN TERMS OF PRE-SELECTED RESISTANCE ACCOMPANYING DESIRED TEMPERATURE IN SAID RESISTIVE HEATER; AND VARYING ENERGIZATION OF SAID RESISTIVE HEATER CIRCUIT SO AS TO MAINTAIN SAID PRE-SELECTED RESISTANCE AND, THUS SAID DESIRED, TEMPERATURE IN SAID RESISTIVE HEATER. 